This application is related to the following pending applications being concurrently filed herewith and assigned to the assignee of the present invention:
This invention relates generally to air conditioning systems and, more particularly, to an air conditioning system for the rooftop of a bus.
The most common approach for air conditioning a bus is to locate the air conditioning components on the rooftop thereof. Inasmuch as power is available from the engine that drives the bus, it has become common practice to locate the air conditioning compressor near the drive engine such that the drive engine is drivingly connected to the compressor, with the compressor then being fluidly interconnected to the air conditioning system on a rooftop of a bus. This, of course, requires rather extensive piping between the engine compartment and the air conditioning unit, thereby increasing installation and maintenance costs.
Another problem with such existing systems is that the speed that the compressor is driven is dependent on the speed in which the drive engine is running. Thus, when the drive engine is idling in a parking lot, for example, the compressor is running at a relatively slow speed which may not be sufficient to provide the desired degree of air conditioning. It is therefore generally necessary to oversize the compressor in order to obtain the performance needed under these conditions.
Others problems associated with such a motor driven compressor system is that the open drive compressor needs a shaft seal and a mechanical clutch, both of which are subject to maintenance problems. Further, since DC power is available on a bus, DC motors have been used for the air conditioning system. In general, DC motors are not as reliable as AC motors since they have brushes that wear out, and brushless motors are relatively expensive.
In addition to the problems discussed hereinabove, it is recognized, that because the wide variety of bus types and application requirements, it has been necessary to provide many different types and variations of air conditioning systems in order to meet these different requirements and vehicle interfaces. As a result, the manufacturing and installation costs, and sustaining engineering resources that are necessary in order to properly maintain and service these units, are relatively high.
Conventionally, bus air conditioning systems have relied on the general leakiness of a bus for purposes of replenishing the air therein. That is, because buses generally have many areas where outside air can leak into the bus and inside air can leak out of the bus, there has been no need to deliberately circulate fresh air into the bus and stale return air out of the bus. However, as buses have become tighter in construction, it has been found that the recirculated air can eventually become stale.
It is therefore an object of the present invention to provide an improved bus top air conditioning system.
Another object of the present invention is the provision for a bus air conditioning system which is effective at all operating speeds of the bus, while at the same time does not require an oversized compressor.
Yet another object of the present invention is the provision for reducing the manufacturing, installation, and maintenance costs of a bus air conditioning system.
Still another object of the present invention is the provision in a rooftop air conditioner for a systemic replenishment of air within the bus.
Yet another object of the present invention is the provision for a bus rooftop air conditioning system which is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, an air conditioning module is assembled with its condenser coil, evaporator coil and respective blowers located within the module and so situated that a standard module can accommodate various installation interfaces with different types and locations of return air and supply air ducts on a bus.
In accordance with another aspect of the invention, a plurality of modules can be installed on the roof of a bus, with each pair, being in back-to-back relationship near the longitudinal center line of the bus.
By yet another aspect of the invention, the modules may include a compressor, such that all the necessary refrigerant piping is located entirely on the module, with electrical power being provided to the electrical components on the module from a motor driven generator.
By still another aspect of the invention, an air mixing flap is adjustably positioned between the condenser coil and evaporator coil such that fresh air can be introduced into the flow to the evaporator coil, while at the same time, a portion of the return air is routed to the condenser discharge opening by way of the flap.
In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true sprit and scope of the invention.